Eccentric screw machines are pumps or fluid-drive motors with a hollow, screw-like stator in which a screw-shaped rotor turns eccentrically around the axis of the stator while at the same time turning around on its own axis. For this combined rotary movement the rotor is linked by a joint to a coupling rod, which in turn is connected by an additional joint to a drive shaft that is supported in a fixed position. The two joints, while the delivery medium or drive fluid is flowing around them, must permit the coupling rod to move angularly with respect to the axis of the rotor or the drive shaft, in continuously changing directions and in orders of magnitude of generally 2.degree. to 4.degree.. In this process the joints, regardless of their make-up, must be securely sealed off from the delivery medium or the drive fluid, if, as is usually the case, the fluid is not suitable for joint lubrication or actually contains corrosive and/or abrasive components.